1. Field of the Invention
This invention relates to an improvement of a film feeding device in a camera in which a film in a patrone is loaded for taking pictures.
2. Description of the Prior Art
In a conventional system of feeding a film with a sprocket, one or two of the teeth of the sprocket are engaged with the film perforations on each side of the film, and the film is fed by rotating the sprocket. Therefore, a shearing force is imparted to the film, and sometimes the film perforations are broken, with the result that the film can no longer be fed. This is a serious drawback in the conventional film feeding system, and especially in an automatic film loading device for a camera. Thus a need exists for a better film feeding system than that of the conventional sprocket system.
Further, in the above-described sprocket system using the conventional engagement members (teeth), as shown in FIG. 8 each sprocket tooth 41 has a rectangular section 44 along the plane of the film 42, like the tooth shape of an involute gear. The sprocket tooth 41 is engaged with a film perforation 43 to move the film 42. Observations of broken films revealed that the perforation 43 broke toward the preceding perforation from the points thereof contacting the corners A and B of the sprocket tooth 41. This presumably occurs because the corners of the perforation 43 cannot easily be deformed and because a stress is exerted on the perforation in such a way that the stress is the maximum at the corners A and B of the engagement member, as shown in FIG. 9. In the case of an automatic film loading device for a camera, the above-mentioned phenomenon tends to occur when the leader section of a film is automatically pulled out of a patrone set in the camera, namely, when the initial film pulling resistance is the maximum. Therefore, even if an excellent patrone setting system is developed, its cannot be utilized to full effect unless something is done to prevent the above-mentioned phenomenon.